On Sat, Jan 16, 2021 at 22:19, Pavel Šimerda <c...@simerda.eu> wrote: > Provide a debugging interface to read and write MDIO registers directly > without the need for a device driver. > > This is extremely useful when debugging switch hardware and phy hardware > issues. The interface provides proper locking for communication that > consists of a sequence of MDIO read/write commands. > > The interface binds directly to the MDIO bus abstraction in order to > provide support for all devices whether there's a hardware driver for > them or not. Registers are written by writing address, offset, and > value in hex, separated by colon. Registeres are read by writing only > address and offset, then reading the value. > > It can be easily tested using `socat`: > > # socat - /sys/kernel/debug/mdio/f802c000.ethernet-ffffffff/control > > Example: Reading address 0x00 offset 0x00, value is 0x3000 > > Input: 00:00 > Output: 3000 > > Example: Writing address 0x00 offset 0x00, value 0x2100 > > Input: 00:00:2100 > > Signed-off-by: Pavel Šimerda <c...@simerda.eu>
Hi Pavel, I also tried my luck at adding an MDIO debug interface to the kernel a while back: https://lore.kernel.org/netdev/C42DZQLTPHM5.2THDSRK84BI3T@wkz-x280 The conclusion was that, while nice to have, it makes it too easy for shady vendors to write out-of-tree drivers. You might want to have a look at https://github.com/wkz/mdio-tools. It solves the same issue that your debugfs interface does, and also some other nice things like clause 45 addressing and atomic read/mask/write operations.
